Definition: In this task, you are given an input list A comprising of numbers and alphabets. You need to extract and sort the unique alphabets in the list. The alphabets in the input list will only be in lowercase. Return -1 if there is no alphabet in the input list.
Input: ['7635', '9281', '5901', 'p', '8791', 's', 'r', 'h', '3579']

h, p, r, s